Catadioptric lenses are well-known in computer vision and imaging systems, robotic sensors, and various other applications. Each imaging application typically has specific design requirements, resulting in many different types of catadioptric lenses. Unfortunately, many wide-angle lenses and optical systems are complex and expensive.
For example, U.S. Pat. No. 6,449,103 discloses a variety of complicated wide-angle lens systems. U.S. Pat. No. 5,473,474 to Powell discloses a panoramic imaging system that is comparatively simple. One embodiment has two spherical refractive surfaces and a single elliptical reflective surface. It is not evident, however, that this system would be useful in certain machine vision applications since the design does not produce the important feature of a single view-point (SVP). The SVP feature can only be produced by a special class of catadioptric lenses and is important in machine vision applications, i.e., performing optical measurements of a scene, because it permits the distortion-free reconstruction of the image. U.S. Pat. No. 6,611,282 to Trubko et al. discloses a folded-type catadioptric lens having an SVP feature. This system would be useful for many machine vision applications, but would be limited in its use for optical ranging applications involving absolute measurement of distances unless two or more such lenses are used in stereo-vision or multiple-view systems that are well known in the art. It would be desirable to have a single, simple, compact, inexpensive lens with a wide field of view that is suitable for optical ranging and similar applications.